Albert Einstein developed the theory of relativity using “thought experiments’’ to illustrate the consequences of a constant speed of light. Many measurements have validated Einstein’s work, but some thought experiments and applications of relativity have only become possible in reality with advances in technology. Technologies where relativity is important include radiation sources such as synchrotrons, free-electron lasers and plasmas created in the laboratory.
Some of Einstein’s and other original thought experiments are now able to be reproduced. For example, the “twin paradox’’ experiment can be replicated by flying accurate atomic clocks. In the twin paradox thought experiment, a twin embarks on a space voyage and accelerates away and then back to earth, returning much younger than their earthbound sibling. In an appendix to my book “An introduction to special relativity for radiation and plasma physics’’, I explore a twin paradox thought experiment where a twin departs aged 20 and returns at age 40, but on earth several hundred years have elapsed. With atomic clock experiments the time differences between accelerated clocks and earthbound clocks is small, but measurable (see, for example, https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment).
It is now possible to perform Einstein’s thought experiment where light is reflected from a rapidly moving mirror. Plasmas created by focusing intense, short pulse lasers onto solids reflect light at a critical density of plasma that moves rapidly away from the original solid surface at speeds approaching a significant fraction of the speed of light. The light reflection follows Einstein’s relativity predictions (see Chapter 9 of “An introduction to special relativity for radiation and plasma physics’’). My book ‘An introduction to special relativity for radiation and plasma physics’ introduces special relativity and explains many of the applications of relativity in plasma physics and radiation sources. The book reviews the underlying theory of special relativity, before extending the discussion to applications frequently encountered by postgraduates and researchers in astrophysics, high power laser interactions and the users of specialized light sources, such as synchrotrons and free electron lasers. I wrote the book because I felt that laser-plasma researchers and users of radiation sources needed a text at an appropriate level that explains relativity and its applications
Author: Greg Tallents